The steroidogenic capacity of fetal gonads will be studied using incorporation of radioactive precursors to determine what metabolic pathways are functioning in fetal gonads. Gonadotropic stimulation of fetal gonadal steroidogenesis will be studied by in vitro and in vivo experiments. Fetal pituitary response to gonadotropic releasing hormone (GnRH) and thyrotropin releasing hormone (TRH) will be quantified. The in vitro experiments will use a perfusion system that bathes pituitary slices from male and female fetuses in medium. GnRH and/or TRH will be added to the medium and the pituitary hormones that are released in the effluent quantified. The fetal pituitary response to GnRH and TRH will be quantified in vivo by catheterizing the fetus and studying the pituitary response to releasing hormones. Fetal hypothalamic LH releasing activity will be quantified to determine fetal sex and age effects on releasing hormones.